What might happen if I don’t get cellulitis treated?

Worsening infection. Cellulitis is a skin infection. Normally oral antibiotics will cure the infection. If the infection is left untreated the infection cold worsen and spread internally into the blood stream. A blood stream infection would then require hospitalization for intravenous antibiotics.Blood stream infections are potentially fatal.
Many causes. Cellulitis is basically a visible inflammation (itis) of the skin and soft tissues (red, hot, swollen and tender) . It can be caused by many things including sunburn (radiation), trauma (sprained ankle) or poor vein circulation (stasis dermatitis). It need not be caused by bacteria. If you have repeated episodes of this, get to a wound care or vascular specialist, the diagnoses you have is wrong.
Worsening morbidity. Untreated cellulitis could easily lead o limb loss and possible death.