If you are totally reluctant to wash the whole piece, cut off a small piece - only needs to be about 1 x 2 inches - put it in a clear glass of hot water with a drop of dawn dish detergent - and let it set overnight.
If your water is clear the next day - you are "probably" going to be okay to use it.
If the water has a pink tinge to it - I would soak the rest of it in hot water that has had some Dawn added to it for at least two hours - rinse - see if the water is clear - if still pink - repeat.
An article worth taking the time to read:
https://www.colorwaysbyvicki.com/sav...g-quilt.html#/
Personally, I soak and wash everything washable before cutting it. I have had enough bleeding fabrics - of all colors - to want to avoid surprises.
However - there are people who have said they have never ever had a problem.