Instagram offers a zoom function in the app by default. Just go to the profile of the user whose picture you want to enlarge and perform the classic pinch-to-zoom movement on your screen. This method can work for some profile pictures, but often there is a limit to enlargement.
There are also some browser extensions that claim to allow Instagram profile pictures to be enlarged. However, caution is advised here as not all extensions are secure or reliable. Make sure you choose a trusted extension from your browser's official extension store.
While it might be tempting to look for third-party apps that promise to make Instagram profile pictures bigger, it's not a recommended practice. These apps may contain malicious software or violate Instagram's Terms of Service, which may result in your account being suspended. It is important to keep your account safe and not to take any unnecessary risks.