Dicky,
Most sanding sealers are based on shellac or acrylic and sometimes vinyl polymers and are designed to make sanding easier, cutting the preparation time for subsequent finishes. They will resist absorption of the oil to a degree depending on how thoroughly they have sealed the wood. BUT remember than ANY finish will seal the wood to a degree, including the first coat of oil.
Therefore to answer your question, you can apply the oil and depending on what oil it is (eg Danish oil or a polymerising oil like BLO) it will perform rather like a second or subsequent coats of the product would have done if you had not used the sanding sealer. You may not get as much "pop" of the grin as you would have done applying oil directly to the wood.
