Going by your description, without seeing your flow, I assume the flow is being started each day by a date time Thing. Leave it set to repeat daily, but control it with a variable.
Have the flow only run if the variable is greater than zero.
Have buttons or commands to run flows to set the variable to the number of nights you want your lights flow to run.
Make a countdown flow that runs at sunrise which decrements the variable by 1 only if it is greater than zero.
To run it one night use a button or command that runs a flow to set the variable to 1. It will run that night, but at sunrise the countdown flow sets the variable to 0, so it won't run anymore.
And you can have other buttons or commands to set the variable to higher numbers for running more than one day in a row.
If you have any other questions about this, be sure to post a picture of your flow, or share the flow.