I'd agree that looks like either an infection of some kind or a burn injury.
A "nutrition powder" isn't very likely to help (or hurt), but an antibiotic cream might- it all depends. I'd also agree about topically using Vetericyn (if available where you are) or Betadine solution (aka povidone-iodine) that's diluted (to look like weak tea).
You also called this a bump- the amount of swelling isn't obvious in the photo, but swelling under the skin does suggest an infection- and it's possible that topical application of medications (no matter how effective they are) won't be enough to remove the infection. Snakes produce solid pus for the most part that requires surgical removal, as it cannot "drain"- but hopefully this won't get to that point.
There is a limit to how much we can help you online- this really does need an in-person vet visit & I'm sorry that your options are limited. I hope your snake recovers okay- pay close attention to see if this increases or seems to be healing- and DO check your enclosure for anything that might have caused this (burn? scrape?). Best would be keeping him on clean paper towels for substrate while he's healing. If this appears to be spreading (increasing in size or area) DO get back in touch with your vet.
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