Hard tender patches appearing after groomers visit (shave, bath and brush)

Took my boy to the groomers last week for a shave bath and brush just to help him with the heat. (+30 degree Celsius) and they mentioned it seemed like he had a couple bruises that were tender while she was shaving him. When I got him he has a spot that seemed a little hard and one that was just darker (both the spots they noticed). At first I thought it was just his hair having been shaved a little different in that spot cause he was tender but over the week he's been liking them and now they're hard and clearly tender - he shivers when they're brushed and if they keep getting touched even very lightly he seems agitated.  they are both on his mid to lower back a few inches above his tail on either side of the spine. At first I thought maybe it was him reacting to human oils but it's not on the areas we pet or touch most it's actually probably in the areas touched least. I can't find anything about it online - there's no noticeable sores or redness (at least that I can see). Other info is: - His diet hasn't changed and he's been on it for almost a year, instinct kitten food - He's about 9 months old - My roommates and I are moving so there's been some stress - He usually has insanely soft fur - Unlike skin anywhere else these areas feel stuck down (like it's not moving off the muscle or whatever would be under it where as the rest of his skin as per usual is slightly stretchy and moveable If you think there's any other info that could help please let me know! Thank you!

Hello -  however that started out, be it an attempt to soothe low-grade spinal or pancreatic pain, or fleas,  or heat-rash or a micro-fissure in the skin from the clippers... and whether it was has become progressed to dermatitis or whether the story is more unusual, it now sounds sore and as though continued self trauma or inflammation might exacerbate the problem.  Skin issues can spread quickly so perhaps call your vets or their weekend cover and let them know how things are progressing.  This should help you to make an appointmemt at an appropriate time to get it checked.   In my experience skin diseases can be hard to get on top of, so its definiteky worth getting it checked out early.

....getting *them* (skin diseases) checked out early.

yes that is understandable at petdisaease.net i saw talk about it too