Beginning signs of Mastitis?

H

My little one is 11.5 months old and Because we were so busy yesterday I skipped a feeding. I noticed my breast started getting sore but I fed her really good last night. When I went to bed, I was freezing. Literally shaking! Woke up in the middle of the night pouring sweat. This morning I noticed that one breast is still tender and has a big red “patch” on it. Is this the beginning of Mastitis? What do I do? 😔