[Parker's Mum]

ok, I had a family member dog-sit parker while I was on vacation. Unfortunately, he didn't get brushed as often as I do it, and all around the base of is tail, his back, down onto his legs got really badly matted. So he started biting and scratching at it like crazy. I did my best to get most of the mats out, but he is still biting at it like crazy. The hair is alot thinner (I'm not sure if that was from me working the mats out or his biting), and it looks red and sore on his skin (at first I thought that was just from me working out the mats, but it hasnt gone away). I've bought some oatmeal shampoo to help relieve the itching but it hasn't seemed to do much. Will this clear up on its own, should I take him to the vet? I wanted to take him to the groomer next week, but I don't think I should until I know what it is for sure. Any suggestions??? Thanks