There are nothing relation to quotation.
See, If you change the price after GR, then system will try to post the price change amount to inventory stock account (material stock account) and it will be causes to MAP change (if you have the total stock exist of GR qty). Then normally no problem with price change in PO line item. You can just see the difference amount is showing in PO history for GR & IR and your G/R clearing account will be showing as per your GR.
If possible, then you can cancel the GR. This will be the best option. All things will be shown correctly when you will have a look into the PO in future.
If you change the MAP price for material, then it will be another question for you and your end users in future (when you will forget about the PO price changes), why you have change the MAP price manually ? Then it will tough to answer the question.
If you do not have the stock for your material, then the rest amount will goes to price different account.