Head and hand wounds bleed and bleed and bleed and it is super common to think your child is going to bleed to death from a very minor injury there. Just about every family I know with more than 1 child has a story about a head wound or cut finger that they thought was super serious and ended up needing a plain old bandaid.
Given difficult child's age, it will probably heal quite well with no real problems and any scar won't be very noticeable in a couple of years. I split my lip open three times in the same spot from ages 6-8 and each time it was deep enough to need stitches. I have a super tiny scar that most people never notice - even makeup artists who are looking at my face carefully don't notice and if I ask they can't find it. Given that this was 3 cuts one on top of the other, each needing 3 stitches and I chewed the stitches out TWICE (they itched and drove me truly nuts), it shows that kids have an amazing ability to heal almost anything.
I would keep waking him up every couple of hours if he had any nausea, headache after a couple of hours, or other signs of concussion.
Butterfly bandages are sold in drugstores here and those are the special strips to help minimize scarring. They don't stretch the way bandaids do. You can use superglue, but make SURE that it is a brand new tube for each injury due to infection risk. I wouldn't recommend it but I know paernts who use it. mostly their kids HATE it and the only time I saw it used the kid said it stung. Given this kid, it probably didn't. I just don't know because I haven't used it. They used to sell a liquid bandaid here and I don't know if they still do. You spray or paint it on and it leaves a clear covering to protect the wound with-o a bandage. I tried the early versions and couldn't tolerate them because they stung. I then read the ingredients and they had a fair amount of alcohol in them.
If he is okay now and it wasn't hurting too much and he didn't have a headache, and he is the same in the morning, then I would probably not go to the doctor. I would make sure that it is treated with antibiotic ointment (like neosporin, polysporin, triple antibiotic ointment, etc....) in the morning and evening for a few days. The ointment will help prevent scars and keep it from getting infected. I don't know if stitches now can prevent scarring. If tomorrow the wound is still open, not scabbed over, it may be too deep to heal easily and then he should get stitches or butterfly strips to close it because it is a big infection risk. this doesn't include if it bleeds a bit because removing the cotton wool takes off a bit of the scab.
I hope J doesn't hurt too much from this and that it doesn't scar.
Oh, if there are any signs of infection like angry redness that grows in area or has red lines coming out of it like spokes on a wheel, or pus, or he starts to run a temperature, then get him to a dr ASAP.
Oh, you might want to find a box of those butterfly bandages at the store next time you are there so that you have them next tme. He will probably do this again on some body part! Most kids do, and difficult children do more than usual. Or mine did anyway!