If you're tasting a hydrometer reading, have no fear. It will mellow.
If you're tasting the beer in secondary, have no fear. It will mellow.
If you're tasting the beer out of the bottling bucket, have no fear. It will mellow.
If you're tasting beer that's in the bottle, have no fear. It will mellow.
There's really only two off-flavors that will never mellow, no matter what you do. Oxidation (soggy cardboard) and infection (pure death, you'll know it when/if you taste it.) Even DMS (corn, or rotten vegetable flavor) will tend to mellow out with age, altough it will always be present. Just a bit of yeast taste means that either the beer needs more time, or that you need to pour your homebrew more gently from the bottle, and discard the last 1/2" or so.