This yellow stuff is known as calculus which is stuck in your teeths from outside and inside which needs to be cleaned asap, or else your teeth will get mobilized soon, you can go for braceles afterward but important is to clean the calculus from a dentist it wont pain and dont use tooth pics, because of this you may face many problems like bleeding while brushing, halitosis,gingival recession, and many more so go for it dont be so afraid
Next Steps
Visit a dentist soon