Hi
Here's a guide we recommend following for cleaning your device:
"iPhone 14, iPhone 13, iPhone 12, and iPhone 11 models
These models feature glass with advanced textured matte finishes either on the back glass or around the camera area. With normal use, the textured glass on your iPhone might show signs of material transfer from objects that come in contact with your iPhone, such as denim or items in your pocket. Material transfer might resemble a scratch, but can be removed in most cases.
Clean your iPhone immediately if it comes in contact with anything that might cause stains or other damage — for example, dirt or sand, ink, makeup, soap, detergent, acids or acidic foods, or lotions. Follow these guidelines for cleaning:
- Unplug all cables and turn off your iPhone.
- Use a soft, slightly damp, lint-free cloth — for example, a lens cloth.
- Avoid getting moisture in openings.
- Don’t use cleaning products or compressed air.
Your iPhone has a fingerprint-resistant oleophobic — oil repellent — coating. Cleaning products and abrasive materials will diminish the coating and might scratch your iPhone."
If you have another model or would like to check out the full resource you can here: Cleaning your iPhone
If you're having an issue with the hardware and need it evaluated you can contact Apple directly for your best options here: Get Support
Take care.