Do I have to file a separate return if I received a W2 from a previous employer for an error in my PTO payout upon leaving and the W2 is only for 38.10?

Yes. Since all tax documents are reported directly to the IRS, it is highly recommended to report this and all tax documents on your tax return. 

I am reporting it on my return, I just didn't know if I needed to file a state return for Illinois since this money was earned in Illinois. The state amount was less than $2.00?

Since there was an effect on the state tax return, it would be recommended to file the return.