I forgot to sign and date my return while efiling. the irs hasaccepted it. what should i do?

When you e-file there is no physical signature.  You "signed" electronically by entering your AGI or PIN.   

You can't forget, otherwise you would not be allowed to e-file.  By giving permission to e-file, you signed electronically, and Turbotax automatically applied the date. 

You are not signing your electronically filed return to the IRS with a normal signature, instead, you are using a PIN, last year's AGI, to verify yourself. Accepted means your tax return is now in the government's hands and has passed the initial inspection, so you won't need to do anything more.  After acceptance, the next step is for the government to approve your refund if due one. Please see the information in this TurboTax FAQ here for assistance.