I was stung by a bee - don't know if stinger is still in - my foot is swelling - what should I do?

See podiatrist soon. You should see a podiatrist soon or go to emergency room for treatment. You can try taking Benadryl (diphenhydramine) which is over the counter.
Treat a bee sting. If you aren't allergic remove the stinger with a metal object (knife) scraping at an angle. The venom sac keeps pumping until removed. Apply ice to reduce pain/swelling. As a beekeeper i've found rubbing the area with a cut onion for several minutes helps. Avoid scratching and apply calamine lotion as needed. Take heart in that your next sting will be less painful!