To measure current, obviously some current must flow, for that you need a circuit. If you're not powering anything in particular you can use a resistor.

If you use a resistor, the voltage across the resistor will also define the current through it.

Note though that the voltmeter will also draw some current (the same way that an ammeter drops some voltage. You can't measure voltage without changing the current, and you can't measure the current without affecting the voltage. However the effects can be small enough that they are of no consequence. In this case, it is likely of no consequence.

The fact that voltage and current are precisely in step with each other makes for a very dull graph. Perhaps you should graph voltage and power? Power generated from your panel is (I^2)xR or I * V or (V^2) / R (all will calculate the same value)

Power is in Watts, which is Joules per second, so knowing the time between measurements you can calculate the amount of energy in Joules that has been captured, and you can graph the cumulative value of this.

If you have access to several identical solar panels, you could use a different resistor value with each and see if that makes any difference to the total power generated over some period. If you select the resistors correctly you will find that different resistors seem to be "better" under differing conditions.

The last finding may suggest a conclusion about solar panels.

If you do attempt something with multiple panels, they need to be close together and oriented the same way so that they receive light at the same angle and so that (as far as practicable) they get the same light conditions.