Welcome to HCM
You have this IUS system in place for 2 years and pain which you felt is unlikely to dislodge the IUS (Coil) .
If you know yourself to check for thread inside,you can check yourself and if there is any doubt then it is better to check with trained person or Gynaecologist.
In case there is delay in visiting Gynaecologist then in the mean time some other method of contraception
must be used.
Good luck to you.