Hi there. It is very possible this lesion is 'friction induced' or aggravated & the primary problem can either be an insect bite (spider unlikely) or some infected gland/cyst
in the region. The hardness & swelling will take a while to settle. I would advice trying a cortisone
cream admixed with an antibiotic that you could aquire over the counter from any pharmacy. If it does not subside, please visit your GP early next week. Cheers & Good luck!