I missed the cellphone power button and pressed my middle finger down hard on the glass.. its red on e tip. can one fracture a finger tip this way?

Well not likely with: Not likely with your scenario. But a bruise seems much more likely. See how the digit feels if issue persists then to the doctor you go for exam

Unlikely : Be careful, and wait till it heals, best wishes

Hardly: Unless you broke the glass I don't think you pushed it that hard. May have sprained the finger. Immobilize it by lightly taping it to the next finger and it should feel better in a week or 10 days.