Based on past experience, lumps and bumps aren't usually something I fiddle around with. As many here already know, Java had 2 lumps removed when she was about 3yo. They were very small upon first detection...I found them when running my hands over her like I do after a routine nail trim. One on her back, in front of her hips, and another on the skin tuck. They turned out to be cancerous but have not returned after removal. The vet believes this is because of being adamant about them and catching it early.
My rule of thumb is to watch it for a week. If no change for the worse or better, watch it for two weeks. If the bump hasn't resolved on its own by two weeks I have an appt made to see what it is. If it grows or changes appearance in any way during this time, I call that day to make an appt at the earliest I can.
If it is a bug bite or odd bump from being goofy, it should go away on its own. Is it red, scaley, scabby or anything? Does it move freely under the skin? Hard or squishy? Don't poke and prod too much other than an initial assessment.
Be sure if/when you do have it checked that they do a fine needle aspirate and possibly a biopsy. A vet cannot and should not 100% diagnose a lump that hasn't gone away as benign without doing this!
Java recently had another lump checked and it turned out to be a fatty tumor that won't cause her any trouble. They are common for older dogs and certain breeds. Not all lumps are bad, fortunately!
Good luck and keep us updated on Mr. Atlas. Fingers crossed its nothing to worry over.