A wound like that you can't use peroxide, it kills newly forming skin cells.
Can you do a warm compress to see if you can loosen some.of the dried blood on his leg? Try the compress on your skin, it shouldn't feel hot, just pleasantly warm, replace every five minutes for twenty minutes, then see if saline can dislodge some of the scab. Then spray bacitryn, once it's a little dry slather with antibiotic ointment.
Repeat three times a day for two days and then you can reduce to two ...see.if.ita looking better, then to once a day.should be mostly healed in two weeks.