Hello,
From the symptoms it can be simple irritation skin or dermatitis skin. You can apply some calamine lotion at the rash as it will help in soothing the skin. Application of mild corticosteroid cream and oral antiinflammatories like ibuprofen/acetaminophen are also helpful. If the symptoms are severe then it will be best to consult a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Maybe the picture isn't doing the spot justice, but this doesn't look as bad as you described. If you're bothered by the redness of the acne scar, look for spot treatments with sulfur, which lighten the skin after a few weeks of use. Also dermatological light treatments are available, but probably wouldn't be covered by insurance, since its considered cosmetic. Also use good sunscreen (looks like you do). But really, it looks like you had a good workout and you shouldn't be embarrassed by the small pink spot.