What's wrong when tic bite dark red n knotted and size of a nickel?

? deer tic. See a physician. This may be the so called "target rash" that heralds lyme disease.
Need magnified exam. Best to see a dermatologist who can examine the bite site under significant magnification to identify if there are some retained mouth parts in the wound, that need surgical removal. The tick-borne infectious diseases will provide reason for close monitoring of your response to the bite, and possible need for additional blood testing.