Hi Basavaraju, 

If you have forgotten your cet exam user id, then you need not to worry about it just follow the required procedures; 

• From your registered email id, write an email and ask the examination cell for the user id. 
• If they don't respond,  write a mail to the main college office id. Ask them about your query. For sure, they will help you out  .

Hope it helps. Good luck. 

Thank you.