It is not very obvious from the photo what the red spot may be. Possible causes of a red spot could be:
Acne papule or nodule
Inflamed cyst
Insect bite reaction
Bacterial infection etc
Signs to look out for would be a spot that is worsening or changing. If the spot is getting larger, more painful or swollen, associated with fever or other lumps, those are generally worrying signs that should fast track you to seek urgent medical attention. Do see a doctor or Dermatologist for an early opinion to avoid worsening of your symptoms. Hope this helps.
