We are sorry to hear of your fall.
During your preparations for immersion, you should soak the scab to soften it. If the scab is ready to come off, you should gently remove it. If the scab is not ready to come off, or it is painful or difficult to remove, you may leave it and it is not considered a chatzitzah during mikveh immersion.
Please feel free to get back to us with any further questions.
Refuah Shleimah!