Move the speaker away, and unplug the set. Leave it unplugged overnight.

This should trigger the demagnetization circuitry when the set is plugged
back in and restore your set to proper operation. If there should be some
residual discoloration left, try the whole cycle again.

If the speaker was particularly large or the actual speaker driver assembly
got too close to the set or its screen more permanent damage may have been
done. This is rather unlikely, but possible if the discoloration will not go
away after two or three cycles.

William