Here are some words that *might* sound similar depending on how you pronounce them:
* Oof (the word itself, obviously)
* Oaf (a clumsy or stupid person)
* Off (away from a place or position)
* Aught (anything at all)
* Oft (often)
It's also possible that you're thinking of a sound that's not a word, but just a similar noise, like "ugh" or "ouch."
Can you tell me what context you heard the sound in? Knowing the situation might help me figure out the word you're looking for!