Just keep a close eye and look out for any signs of RI (continue doing what your doing). When he yawns is it over and done with pretty quick or does he leave his mouth open for a second or two? you said he yawned while you had him out and maybe after he just woke up; those are both times where ball pythons might just yawn, sure its something you need to watch...but as a new snake owner you can stress yourself out for nothing. take him out and let him exercise, before you put him back turn off all things that make noise and hold him close to your ear listening for popping/wheezing. After you put him back in his set up watch him for a few min and see if he does a long drawn our yawn, if he’s holding his mouth open for any length of time you may have something to worry about.