Not a nurse, but do have experience in dental. The general rule of thumb when dealing with changes in the mouth is, if it lasts or has persisted for more than 2 weeks, you need to see a dentist. Most things clear up or begin to get better within that timeframe and if it hasn't or gets worse, you don't delay. You don't ignore it.

No one can diagnose you over the net, only an in person dental or doctor appointment will answer your questions or allay your fears. If something doesn't look quite right, they will take a biopsy of the affected areas. This is either done by a dentist or an oral surgeon. Requiring a biopsy doesn't mean it is cancerous, it just means they have to rule it out.

okay thanks for replying, do you think by saying what i have said that it is anything bad? I am only 14 years old

Your age is greatly on your side that it's nothing, but if you have had a recent virus, especially tonsillitis or covid, that can do weird things to your mouth. But if it lasts for more than 10-14 days you do have to say to your parents and they would have to take you to see a dentist or doctor. That is important regardless of age.

It could be numerous things, not all sinister in nature. Autoimmune conditions can affect the mouth, as can viruses and poor dental hygiene. Non-healing white patches need to be checked after the time frame i've given you above as do lumps.

Your age is greatly on your side that it's nothing, but if you have had a recent virus, especially tonsillitis or covid, that can do weird things to your mouth. But if it lasts for more than 10-14 days you do have to say to your parents and they would have to take you to see a dentist or doctor. That is important regardless of age.

It could be numerous things, not all sinister in nature. Autoimmune conditions can affect the mouth, as can viruses and poor dental hygiene. Non-healing white patches need to be checked after the time frame i've given you above as do lumps.