Is it bad to have your stitches fall out of your upper mouth on left side after wisdom teeth removal after 3 days?

Usually not: The first 3 days are the most critical and as long as you are careful, it shouldn't be a problem. Some stitches do not actually fall out but dissolve. It is always best to check with the dentist who placed the stitches.

Not bad: Do the prudent thing, call your Surgeon. You should be OK, especially if surgeon used resorbable sutures, but let him/her decide.