I've Taken In A Stray Cat About A Year Ago

I've taken in a stray cat about a year ago but recently he's ran a way for about 5 days and came back leaking blood from either his anus or penis. When i checked his litter box there was a black worm coverd in blood. so i let him leave to not risk infecting my other cat but now he's come back and with a hole leaking puss from his face what shoud i do.