It's probably fine. I have found tofu to be pretty sturdy. Is it plain tofu or baked/marinated in some way? Tofu gets a real sour smell and tangy taste to it when it goes bad. Taste a little tiny bit and if it's yucky then pitch it. But it's only 4 days over, so my guess is it's still good.
I'm basing this on my experience with packaged tofu (either baked, water packed, or long life tofu in boxes). If it was fresh tofu from a bulk container (i.e. it was in a tub of water and you picked a chunk out), that stuff goes bad much more quickly and I would use it immediately after purchase.
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