Well, if the lump immediately coincided with feeding then I'd be pretty confident that it was just slow digestion rather than something nasty that was unrelated to feeding.
If it was constipation, then I'd expect the lump to be nearer the vent.
Is this the snake's first meal of 2 large pinkies? If so, then their digestive systems can sometimes take a while to gear up to cope with the new food size.
Is the snake due to shed? Again, this can slow digestion as their systems divert evergy into the shedding process.
Otherwise, I'd just double-check temps on the floor (too warm or too cool will interfere with digestion) and if they're good then just sit tight. I'd suggest not disturbing the snake any more - a regurge this late after feeding probably wouldn't be a good thing.
Hopefully others can offer more ideas and advice. Good luck - keep us posted.