The problem size N is the length of nums.
The way to decide asymptotic runtime from code where there are only for-statements is pretty straightforward.
Asymptotic runtimes are described by traditional notation like
O(N)
Which is one simple for-statement. We need to process the input elements only once.
Nested for-statements like you have means we need to check the value of each nums more than once.
You are repeating N times in the outer loop. You are repeating a number of times dependent on N in the inner loop.
Also how do you print a triangle like
*
**
***
****
*****
******
The number of elements in the triangle is proportional to N²