Pain during intercourse is rarely only about size. It's usually about how relaxed and aroused your body is, and lubricant alone doesn't always fix that.
Next Steps
Slow down, use more foreplay and lubrication, and stop if it still hurts. If the pain continues over a few tries, please see a gynaecologist.
Health Tips
Don't push through the pain repeatedly, since that can make it worse. A gynaecologist can check for other causes like vaginismus or infection.