Pink lump on Bull Arab X puppy

This strange lump appeared on my male Bull Arab puppy this weekend, 4 days after getting shaven for ultrasound. Coincidence or something to worry about? 

Hello!   Shaving a patch of hair does not, in my experience, make skin lumps more likely to appear.  I wonder if the shaving exposed something that was previously hidden by hair in that spot, or whether perhaps this lump wasn't noticed at the time, or has come up abruptly since.  Either way, it should be treated like any new lump:  ask the vet to check it.  Extra nipples, infected follicles, tumours (benign or aggressive) may all be possibilities.  You don't explain what the scan was for in the first place so it's hard to comment on whether it could be related to that.  Your vet may want to take a sample to determine the cause.  Please do let us know when more is discovered about it!