What Is The Treatment For Swollen Painful Foot?

I ran my first marathon yesterday. It rained for the first 12 miles. My foot began to hurt about mile 18, but I knew the pain wasn't going to stop me. When I got done and home, the bottom of both my feet had a raised area on them. I think its a blister but its the same color as the bottom of my feet. Not red or a gross color like some photos I've seen. What would you recommend I do to be able to walk tomorrow, I'm off today. I finished 6:37:22. I'm 6'5", 325, 40yoa, good health. No allergies.