Doesn't "Ouch!" mean "I am experiencing discomfort", which is a proposition?
If we can make an equivalence between "Ouch!" and the claim "It is the case that Person X is experiencing pain", then "Ouch!" is a proposition. At the most basic level, a proposition is something that asserts a fact about the world. On a pedantic level, every utterance can be converted to a claim and a proposition. But a question that follows is whether what is said is meant to be propositional in nature.
During the earliest era of the philosophy of language, the answer would be no, "Ouch!" is not a proposition as it does not assert anything about the world. Everything needed to be converted into claims and anything else needed to be thrown out.
It did not take long for philosophers to recognize the problem with this. Ludwig Wittgenstein looks at this question in Philosophical Investigations and spends quite a bit of time trying to unpack precisely what this sort of claim means (or else we just have some arbitrary notes we're mistaking for something).
There's some argument as to what he means by it, but the basic problem is that I feel sentences are not exactly verifiable claims about the world. As one of the other answers suggests, there is a senses in which it is true that I am not trying to make a claim, I am more so reacting to something I am experiencing.
I think a better solution is to recognize that we make many types of utterances, which can bear meaning even if they are not identical to propositions. This is a fundamental benefit from incorporating Speech-Act Theory -- recognizing that some utterances are meant to accomplish things. Expanding on this a bit, there's Herbert Fingarette's Confucius: The Secular As Sacred which looks at how rituals without words form the Confucian tradition can also be meaning-accomplishing.
The term ‘proposition’ has a broad use in contemporary philosophy. It is used to refer to some or all of the following: the primary bearers of truth-value, the objects of belief and other “propositional attitudes” (i.e., what is believed, doubted, etc.), the referents of that-clauses, and the meanings of sentences.
By itself an utterance such as "Ouch!" does not carry a truth-value. Contrast "If I am experiencing discomfort, I will eat painkillers." with "If Ouch!, I will eat painkillers."
That does not mean that a proposition cannot be derived from such utterances, the absence of any utterance, or utterances that convey the opposite of what is being stated (as is the case with sarcasm). But such things come under the purview of pragmatics, not semantics.
This is why the following is plausible:
Bob: I'll get the first-aid kit.
Ouch! is not an opinion or assertion, it is usually a choiceless verbal sneeze.
Ouch! is more like a hybrid physical-mental reflex than a decision to speak.
"I am scared" or "I am uncomfortable" are some of the highest order propositions, invoking "I am" which is to say, "I am to be afraid," or "I am to be discomforted." Those are ultimate statements. Those declare a state of being... they look inside the self and return with a shipping manifest of internal cargo.
Ouch! is like yelling
aaahhhh! or screaming / shrieking except it is an English word, sort of.
It's up there with
argh! ... you know, unfiltered emotional or mental statuses, often attached to some sort of physical event, or a tacit situational queue.
About involuntary physical reactions, one which is less of a physical-mental hybrid can be sneezing and not get a ticket for some traffic violations because sneezing is largely involuntary. Similarly, the majority of uses of
Ouch! are without thought at all, and even take a lot of control to suppress. There is not really a value judgement being made, or a rendering of a feeling into words, like an "I am..." phrase.
Ouch! isn't even really an utterance, it is not truly 'expressed' like
Dammit! may be, in anger.