All property, including money in the account, which remained with the testator at the time of his death, is included in the inheritance mass and is due to all heirs.
Your husband’s son is an heir by law and has the right to a certain part of the inheritance.
If he declared his rights to the inheritance in the manner prescribed by law, then he has the right, among other things, to part of the money that you withdrew from your husband’s account after his death.
In order to give you specific advice on how to act in this situation, we need additional information (whether or not an inheritance case was opened with a notary, if so, who declared their rights to the inheritance, whether or not a will was drawn up, etc.).