My employer messed up box 12 code DD on my W2. That is understated. Do I have to wait for a corrected W2 or can I file with it the way it is?

Yes, you can file your return. Box 12, code DD is the entry for the cost of employer sponsored health coverage. There is no place to enter that value on your tax return, so you can file your return with the W-2 that you have.

Is it okay if this number is grossly inflated on my W2, or should I ask my employer to correct it?

@yooris911  Why do you think box 12 is overstated?  What is the code?  DD?  Yes ask the employer.  It may be right and include other things you aren’t including.