Positive or negative PPD test

Patient: I had a PPD implant done on Monday. I had it checked 48 hours later on Wednesday, the results were negative. But five days after the initial implant, and 3 days after it was read, I noticed the injection sight was raised and red, it is not itchy or painful. I measured it, it’s diameter is roughly 5mm. Should I return to the doctors, and consider this a delayed positive reaction, or could this just be a antigen independent immune response where my body is riding itself of a foreign substance.

Symptoms: Raised slightly red bump at injection sight.