I have a dime sized spider bite. Red lump white center. It is itchy but not painful. How should I care for it? When should I worry?

See below. Wound care with cleaning with soap and water is sufficient to treat now but watch for redness, increased swelling, warmth, and pain or oozing purulent (pus-like), red streaking away from the area or necrosis (black dead tissue) developing in the center of the wound and spreading out circumferentially, then seek immediate medical care.
Not a spider bite. Spider bites in the usa are incredibly uncommon. They are often called spider bites, but unless you actually saw the spider (black widow or brown spider), this is highly probable to be an methicillin-resistant staph aureus infection. Please see a doctor and have this lanced and cultured and managed appropriately.