Hi I Am A White Male 60 Years Old. |I

Hi I am a white male 60 years old. |I am also a Type II Diabetic. About three days ago I washed my dog in our bathtub. While doing this I was kneeling with my left leg under me. The next day I noticed a red discoloration on my left leg. It has also swollen. The area is not very painful at this time. It does look like it has gotten worse sine I first noticed it. Any ideas what this may be?