Pruning back the stem that is leaning the most would be a good idea. Cut it back to the point where you would like to see new growth emerge on that stem. You can prune more than one stem if you want.
Pruned off stems can be rooted, even in the same pot. Leave about 4-6 inches of bare stem below the lowest leaves and insert it in damp soil or in water.
You can also straighten the plant by pushing the main trunk (cane) until the upper stems are more vertical. Pack the soil in tight around the base of the main cane to hold it in place.
Finally, turning the plant so that the weaker side grows more toward the light will also help.
Ultimately, some pruning will be necessary as it will just continue to grow taller and lean more.