I lost mine completely with covid for a couple of months and it was slow to come back, that wasn’t like congestion though, it was like a switch being flicked. For up to a year after I had distortion, but eventually it came back normal.

During this time I was told to sniff and taste strong things, like lemon slices, coffee, mint.

If it’s the type caused by congestion you could try things like inhaling menthol vapour or menthol sweets/gum.