Common words:
* within
* thin
* fin
* sin
* pin
* win
* bin
* tin
* spin
* twin
Less common words:
* sphinx
* flinch
* impinge
* inkling
* intimate
* infamous
* inhabit
* insecure
* insincere
* intense
Words where "in" is part of a larger word:
* rain (within "raincoat")
* pin (within "pinball")
* tin (within "tin can")
Do you have any specific requirements for the words you're looking for? For example:
* Minimum length?
* Specific part of speech? (Nouns, verbs, adjectives?)
* Specific theme? (Animals, colors, places?)
Let me know and I can give you a more targeted list!