Suggest Treatment For Swelling On Left Hamstring And Leg Pain Post Injury

On my morning commute, I slipped and fell down a stair with the majority of my weight landing on my left hamstring (in direct contact with a stair). It swelled immediately and radiated pain through my leg and is now (6 hours later) sore to the touch but I can walk normally. Would heat or cold be appropriate treatment, and is there anything else I should do to ease the healing?