I scratched an itch on my thigh 3 days ago not hard the next morning i woke up to a baseball size bruise with 17 quarter size bruises around it day 3 there is even more bruises and large knot under the biggest one should i be concerned?

You should have it looked at by a doctor. If there is no further injury, there should be no further bruising. Are you certain you did not injure it again? If not, see a doctor to evaluate it. You may need to have some blood work checked. Good luck!

The knot under the bruise is a subcutaneous hematoma ( blood clot) which may harden or eventually dissolve. Do you have a history of easy bruisability,bleeding gums or other bleeding tendencies? Do you take aspirin or Advil type products often? These promote easy bleeding. To get so much ecchymoses from scratching, I wonder if you scratched over a superficial vein. See a hematologist as needed.