He got some bites taken out of the edges of his abdomen. If they suffer any injuries right after a molt, they often don't color and sometimes sclerotize fully (I'm not sure exactly why). Aside from making this instar a little longer due to the extra growth he'll need to do to fix it, there shouldn't be any long-term effects.
I have a now-adult female who was bitten like this, but on the metathorax, when she was presub; apparently that area looked just as yummy for her subsequent molts because instead of getting repaired, the damaged area grew slightly. It's mostly just a cosmetic thing although this female is significantly shyer and more skittish than the others (maybe it still hurts a bit). I've had others with the same injuries who pick less conspicuous molting spots and do fine, though.
