To draw proper V-I graphs we would need experimental readings of V and I for a constant R.

We suggest you try this yourself, here's how to do it.

Take five different values of V (take this common for both Copper and Nichrome)

Now, here R value is important as this would be different in both cases but unique to Copper and Nichrome. Here we are onlychanging V (which changes I) and not R.

we know that

R = ρL /A   (1)

keep L and A same in both case to avoid unnecessary confusion (teh values are upto you)

Now, for copper ρ = 1.68 x 10-8 ohm.m

and for nichrome ρ =  100 x 10-8 ohm.m

So, by using (1) we will have the resistance values of copper and nichrome respectively. 

Further.

Now, using 

I = V/R   . (2)

calculate the current I for a know values of V and fixed value R. Use five different values of V to get five corresponding values of I. Remember that V can be chosen by you and keep it same for both cases (all five values) for better comparison. The only thing that changes would be ρ and the calculated current I.

Now,

Do the above process 5 time for both cases and plot the corresponding V vs. I graphs (for five points).

You will notice that the graphs would be straight lines but with different slopes or tilts.