Bug bite or some sort of acne? Emergency please help me?

There is a bump a slight raise of skin. About the size of the tip of my pinky Its on the sudd if the top if my head. There's only one and it aches when touched bug not slot it's a nuisance bug not excruciating. Only when pressure is applied. But I can feel where it is with out touching it. Like it's presence Is known. So help md out. If it is a bite, what do I do. I have A importance trip and I'm flying half way across the country next saterday. What steps should I take. I'm nervous