For years i've had many countless "grains" underneath my skin on the lower arm. At concentrated parts they resemble cellulite, and seem to increase as i age (i am 22). They rather resemble fordyce spots
but on the lower arm. Almost unnoticeable unless pressed on, and they do not itch/ bleed etc. Sometimes they seem to darken under my skin. I do not think it's Keratosis Pilaris.
hydroxy acids and urea may be used to temporarily improve the appearance and texture of affected skin.
If the symptoms persist then please get an evaluation done from 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.