Speedometer Malfuction

Hello I have a 92 Buick Regal and my digital speedometer is not working correctly, it says that I am going like 112 on the freeway when I am not or 25 when I am barely going 10. I had this problem once before and it fixed itself in a few days, but this has been happening for almost 2 weeks. If there is anyone who can assist me with the problem by letting me know what to do or why this happens your help would be greatly appreciated.

Thank you in advance
Katrena