What counts as a "deep" wound? or "large"? basically, when would i need to see a doctor for a wound?

Depends: Where is the wound? How did it occur? How long has it been there? Is there a discharge? Are you diabetic? In short, if you have any doubt, see a doctor to make sure it is healing well and also to determine if needs stitches or other treatment.

Deep wound: We worry about "deep" wounds for 2 reasons. If wounds are deep enough they might get infected with bugs that grow in low oxygen environments (anaerobes). One of the most serious of those bugs is C. Tetani causing tetanus or "lockjaw". If you got immunized with tetanus shots you're safe. If you get a puncture wound wash wound well! Also, if deep may have damaged deep structures. See your doc!

When to go to a Dr?: Is the real question as sometimes small or superficial wounds require medical attention. If there is ongoing bleeding, a big tissue gap, you have sensory or functional problem, or if it is in a sensitive area you might want to seek help. Common sense rules.