Birth Control & No Period

So this is my second 3 year round on nexplanon. It's been about 3 weeks since I got the second implant put in. Me and my partner had unprotected sex a couple since last week. I'm afraid I didn't wait long enough or that the implant might not be placed properly. I'm having light pink spotting and I'm scared i might be pregnant. Can it be side effects of the birth control or should I be worried?