What Causes Intermittent Pain In Ribs After Getting Hurt?

Hello,
Ive been feeling a pain on my left side for about a little over a week now and im starting to get really worried. Me and my brother were wrestling around all in good fun and we both fell on our side over a large tree stump. Later that day I started feeling pains on my side and assumed i fractured a rib. Its been over a week now , theres no bruise , the ribs feel intact , however the pain is getting alot worse and im pretty sure its coming from my lung cuz its on the inside of my ribcage. What at the time felt like an isolated minor pain has now turned into alot of pain and it feels like the whole lung. It doesnt always hurt however. The pain comes and goes . Ive gone entire days without it, sometimes it hurts for over an hour, sometimes only 10 minutes. Any advice or input would be greatly appreciated. Thank you