Please post photos for better diagnosis.According to your description it might be due to 3 reasons.
1.You might be having nail biting habit.
2. You might have irregular teeth arrangement
3.Your brushing habits and type of the toothbrush might cause this, but this might be rare reason in this age.
Next Steps
Please visit the dentist and find out the cause and proceed with the treatments
1. Habit breaking appliances
2.Ortho treatment like braces or clear aligners.
3. Professional cleaning along with following proper brushing technique with soft toothbrush
4.If needed gum surgery advisable for cosmetic reasons.
Health Tips
Please don’t delay the treatment
Hope this helps you sir