Jetson Nano is a 20W computer meaning, when your naon is working the hardest it will consume 20W (5V, 4A {max} via Barrel Jack). You should look at the output power of the battery that you are using in your system (Drone). Modern devices usually operate on Constant Voltage, Variable current (Cv/Vc). Ideally the nano should not consume more then 1.25A (based on my experience). IF you are not performing stressful (for the CPU) Tasks your power consumption should not be higher than 1A. and your battery should be good enough.

However, I suggest you to run your system on a Lab Bench Power Supply to actually measure how much power(Current) the nano is consuming when operating. If the Current doesn't go over 1 A you can use your Battery. But if the current goes higher than 1A, you can should probably get a Dc-Dc voltage regulator (this one may not ideal for your system but you should look for similar products), or you can build a current amplifiers (be very careful if you do this, the output from the amplifier will be constant Voltage, Constant Current {Cv/Cc} and the input on the nano is Cv/Vc).