Small growth next to plant

It's a stray seed in your soil.

 

I see no point in letting it grow.

 

A clover maybe?

 

I only used one seed per pot in my first grow and in 5 or 6 out of 30 pots I had this issue. I let a couple grow out and it is most certainly a weed plant. on a couple of pots I just pulled it out and it regrew 2 more times. (indoor grow) One of them even got to 5 or 6 inches tall. My plants didn't seem to be too affected by it long term wise