Hi My Husband Has Had Bowel Cancer And Has Now

Hi
My husband has had bowel cancer and has now got a colostomy bag so his body has beenl thru a serious operation in the last few months he has complained of stabbing like or being bitten by a wasp feeling in his penis and area between his anus it does seem to becoming more frequent we have been to the doctors but they just keep giving him more pain killers which really dont help

Can you give me some guidance as what this could be and how to treat the pain