Possible mass on dog’s side

[Helixs_momma]

Hello all,

My dog is a five year old mix (most likely Australian Shepherd and fox hound). He is approximately 55lbs. Over the past few days, I have noticed a slight bulge in is skin on his abdomen area but in front on his left back leg. I have posted a picture for reference.

I’m not sure if I’m crazy or if this is something I need to alert the vet about. Of note, he laid down in the middle of his walk the other day (highly unusual). The spot does not appear tender to him though.

Any insight or thoughts would be appreciated!