Thanks for providing more information.
Well as it is bruising and pain is unbearable so in my opinion,you shouldn't ignore your symptoms and a clinical examination by your regular doctor and further chest x-ray to rule out rib fracture at first place.
Other possible cause may include Intercostal muscle strain.
Apply an ice pack 20 minutes of every hour for the first 2 days.
You may need prescription pain medicines (narcotics) to keep your pain under control
For pain, you can take ibuprofen (Advil, Motrin).
Having said this,consult your doctor or visit ER ASAP for prompt management.
I hope this helps.
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