I have a very uncomfortable rash/cut below my tailbone and above my...What could it be and how do I heal it?

Intertrigo. Intertrigo (intertriginous dermatitis) is an inflammatory condition of skin folds, induced or aggravated by heat, moisture, maceration, friction, and lack of air circulation. Intertrigo frequently is worsened or colonized by infection, which most commonly is candidal but also may be bacterial, fungal, or viral. Intertrigo commonly affects the axilla, perineum, inframammary creases, and abdominal.
Get it examined. Your primary care doctor can examine, diagnose, and suggest treatment. There are multiple possibilities including psoriasis, herpes infections, cyst, eczema, fungal infections, bacterial skin infections, abrasions...