Unable to find photos on my iPhone after password reset

You didn't tell us much. For instance, do you use iCloud Photos? If so, maybe you are not signed in to the same account you were using before the change. Or it could be that your Photos app hasn't had time to download the pictures. How long have you waited?

Some other things that it would help us to know…

• What model is your phone? What iOS does it use?
• Are you using iCloud Photos to synchronize your devices? If so:
• …Do you have “Optimize Storage” checked in Photos’ Settings
• …Do you see all your iPhone pictures at iCloud.com?
• …Do you have more than 10% free storage on your iCloud account?
• Do you have more than 10% free storage on your iPhone?

But we need to know the source of your photos - could you please answer Richard's questions? It'd depends on the way the photos have been imported to your iPhone how to recover them.

• We need to now, if you have been using iCloud Photos, because you might be able to download the photos again from iCloud.
• if you did not use iCloud Photos, but have made regular backups, restoring your iPhone might bring your photos back.
• If your photos have been synced from a computer with iTunes or from the Finder on a Mac, you will have to sync again with the same device.