First of all, please accept my condolences upon the loss of your spouse.
The FL Bar has a great pamphlet, as do most state bars, on the probate process.
Here is the link:
Consumer Pamphlet: Probate In Florida – The Florida Bar
You and the decedent (your spouse) held a joint bank account together that carried rights of survivorship, upon her death, the account belongs to you.
You aren't legally able to deposit a check payable to the deceased into the account, because your spouse's name was removed upon the death of your spouse.
If the check is payable to the estate of the deceased, or payable directly to the deceased, you should open an estate account rather than deposit the check into an account you formerly held together.
Normally an executor manages the decedent's assets.
Upon the death a spouse one of the first things the surviving spouse must do is to set up an account for the estate, if he/she is named the executor. The executor uses this account to pay the decedent's bills and to receive any payments to the decedent or her estate. This account is where the executor deposits checks payable to the deceased. The executor or co-executors are the only ones who can access the account.
In your case, it is often simpler to contact the issuer of the check and see if the entity will reissue the check in YOUR name. That is the proper way to handle the instrument to avoid probate.
However, if the check were intended for her use towards her medical needs, that may no longer be an option. The check might need to be returned to the issuer to avoid legal issues. Before doing anything, I suggest you speak with the issue about how you should proceed so as not to step into legal hot water.
I wish you all the best as you mourn the loss of your spouse. God bless.