Generally cycling would not create it. If it is painful, well there could be a deep lying infection caused by piercing by needle or sometimes internal reasons too. But you haven t mentioned any needling etc. If your saddle is not comfortable, mild concussion etc may also cause it temporarily and would go. In any case it s not a case to worry until it pains that you have mentioned that it pains. It could be infection. But the there should be some fever too. Wait and watch if size and pain increases. If so, you can t do much except killing the pain and let it mature finally to be drained. Once pus formation takes place post infection, it has to drain. Hot fomentation may be done. May use Haridra capsules ( turmeric) as antiseptic/ bacteriostatic. Pre pus formation infection may be managed by antibiotics too. Hope you are worriless now and this info helps you to decide to meet your doctor.