You’ve developed the skills necessary to call on fire to serve your commands. You gain the following benefits:

• Whenever you cast a spell that deals fire damage, you can cause flames to form an arm. Those flames exist for 10 turns. The flames don’t harm you or your possessions, and they shed bright light out to 30 feet and dim light for an additional 30 feet. 
• For its duration you can cast Control Flames at Will

At Higher Levels. When you deal fire damage using a spell of 2nd level or higher, you gain 10 extra turns for each additional level above 2nd.

At the end of each turn, you can make a Concentration safe DC 10. On a failed save, the flames continue but you lose the ability deactivite them, until the next turn. On a successful save, the flames continues to obey you and can be extinguished.

It semes those flames have a will of their own, you are far away of controlling them. Maybe with time you unlock the hidden potential.