I masturbated more than once in one sitting with no lubricant and I don't have foreskin and now I have a red bump on the head of my penis. Treatment?

Here are some ... Based on what you described, it's reasonable to leave your penis alone but keeping it clean and dry without further physical stimulation for at least 5-7 days so to let the Nature heal what you incurred to your penis as long as getting better day by day. If not, seek pro-evaluation & counseling timely.