Child done with circumcision, has repeated occurrence of purple and black bruising on the base of foreskin. Cause?

Hello my 4 yr old was circumstized last year as his foreskin was very tight tonight he complained when he sat down so I asked him to let me see...... On checking him he a some discharged which he often gets but once I cleaned him under it was purple & black bruising at the base (up the top) under the foreskin........ Discharged I m can deal with as he sometimes gets my concern is the appearance of bruising........ Do you feel it is being restricted or is his penis finally dropping & coming out & perhaps he has torn it some where.....??he is quite happy for me to clean it without any fuss or tears .... I was going to take him to women s & children s what do you think. Kind regards