What do I do? I don't have access to the number it's sending the security code.
There are two more method to reset password other than phone number:
- Using email address
- Using Facebook account
If you don't have access of these above two also then don't try from web. Use Instagram app and get help. From Instagram Help Centre:
If you can't remember your password, you can reset it using your email address, phone number or Facebook account. If you're not able to reset your password this way, open the Instagram app for additional help.
This answer explains how to reset password from Instagram app.