The other answers on here seem a bit condescending. Let me try to help.

First off, for 2020 and going forward, you will just file as a sole proprietor on schedule C (or E if it's a rental). Easy peasy, no extra steps.

However, for 2019, your 1065 is probably already late. The partnership terminated when you bought out your partner. The 1065 is due the 15th day of the third month after termination. For example, if you bought out your partner in April, your 1065 is due July 15th. All the activity after the buyout should be reported on your 1040.

That's the technical answer. In practice, as long as you report all the activity, and mark your 1065 final, the IRS probably won't care if you dissolve in December vs April.