Post SkinPen and sun exposure, can sun exposure cause hyperpigmentation?

This is difficult to predict, but it sounds like you used adequate sun protection. I recommend following up with your Doctor for after care recommendations. I recommend prp, PDT after therapy with topically applied growth factors. I also always combine microneedling with prp and lasers to get the best outcomes. See an expert. Best, Dr. Emer

After a SkinPen treatment it is recommended that you stay out of the sun. The skin needs time to heal and can be more prone to burning as well as hyperpigmentation. It is good that you wore sunscreen and wore a hat. For the remainder of the healing period be sure to closely follow your post care instructions.

There is a possibility that you may see some hyperpigmentation.  Ideally, I instruct patients to stay out of the sun for 2-3 days as you heal.  I recommend that you discuss with your provider your concerns.  He or she may prescribe a prescription-strength fading cream for prevention.

Diagnosis is uncertain- Skin Pen and microneedling has no energy, unlike lasers or RF. The induction of PIH and stimulation of melanocytes (pigment cells) is limited. Having said that PIH can occur (less probability than with lasers). Question begs - what was the aim of microneedling? Did you have dermal melasma prior?