The reason I ask is I've made several wines which have turned out fairly bitter. I made a blackberry wine that was very bitter and I contributed it to leaving the seeds in too long. I have now aged that wine for over 2 years and it is fantastic with very little bitter flavor left. My experience is aging certain wines will help the taste. Some people say to backsweeten the wine to reduce the bitterness. I've found that sometimes this only makes a sweet, bitter wine. I would stick it in a bottle if you already haven't and wait it out.