It might depend on your use case and the architecture and there is not a straightforward approach to concatenate two tensors with different shapes and number of elements.
You could repeat the values of the smaller tensor to match the number of elements of the bigger one, but you would of course have to check, if this approach is working and valid for your model.
Alternatively you could also try to reduce the number of elements from the bigger one.
What is your use case and how should the result tensor look like?