Winstrol and Sore Injection

I am currently doing my second cycle of Winstrol that i got from a reliable source which i used before. The last i used i had no problems side effects of anykind.

The day my first injection of .5cc; in 1.5 inch redius a reddish and warm to the touch cirle developed. The injection site is not large or bulbus and neither is this area. But is a little sore and warm, and a light fever accompanied it. Ive heard it may be a reaction or infection so ive scheduled a appointment with the Doc. But i dont understand why if ive already had this gear in my body that a reaction would occur.

Any advice or answers