Is this on Canson? Assuming so, one thing you could do is brush or lift (with a kneaded eraser) off some of the pastel, take some pieces of paper and place them over the barn and background areas -- around the blob -- to protect them. Spray the blob lightly with fixative. Possibly a few coats. Then you can add some sky areas without getting mud or damaging the paper with brushing and/or erasing and can accentuate the trees more afterwards.
The blob looks heavy, so I assume there's a lot of pastel there?
If it's a sanded paper, just scrub off the areas you want sky to show. No fixative needed.
Just an idea.
PS. This painting is looking real good!
<FONT face="Script MT Bold"><FONT COLOR="#AB4835"><FONT size="5">Roan</FONT s></FONT c></FONT f>
<FONT COLOR="#8A1010">Call caraid tadhal tric, 's call caraid tadhal ainmig.</FONT c>
-- <FONT size="1">Friends are lost by calling often, and by calling seldom.</FONT s>
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[This message has been edited by Roan (edited February 20, 2001).]