hi..thanks for the query.
I think the itching that you mention,as well as the pimple ,should not have any relation to the cycling that you are doing.There are several causes why this can happen, most commonly ,the itching may be a result of a
contact dermatitis due to any external agent that might have come in contact temporarily.You can apply a mild
topical steroid for the same for a few days.this should stop it completely in most cases.Try and use clean
inner wear always.You should also take a course of oral anti helminthic /anti parasitic tablets , as a few parasitic nfestions of the gut may cause a similar itch.
As for the small 'pimple' you see, it may be a folliculitic eruption which is a bacterial infection.Hence apply
topical antibiotic cream eg.Mupirocin/
Fusidic acid for about 10 days and see if it resolves.If it is still there, there might be a possibility of a small cyst ( e.g.. sebaceous cyst etc).If so,you can see a
dermatologist and get it removed by electrosurgery or any other suitable methods.
Hope this helps..take care!