Just Starting... BM ?

After months of just using the potty here and there for fun, we have just started PTing without a diaper and have worn underwear or gone bare butt for most of the past two days.  DS had one pee accident the first morning at home and then none the rest of the 2 days while at home, but he managed to BM that 1st morning before we "started" and then the 2nd morning he kept holding his bottom and tried to go #2 but got only a "squirt" in the toilet and then had the BM  in his diaper after nap.  So my questions, will it hurt him if he is holding in his poop?  how can I encourage him to poop without being too pushy? and when did you do away with diapers and nap and bedtime compared to when you started PTing?