It is not pimple, it is a epitheloid cyst
It may be infected and become red.
There may be irritation causing erythema
which you have.
You consult dermatologist
Antibiotics and anti inflammatory drugs will alleviate infection.
After that, cyst may be excised under local anaesthesia.
For that , you consult surgeon.
Do not worry, you will be alright.
Dr. Ilyas Patel MD