You should cover the seed with .5 inches of moist soil. The seed first cracks a little, then a single root tip comes out, then the shell softens as the seed is pushed up out of the ground. Then the shell breaks off, partly due to pushing through the soil, and partly due to the seed leaves (cotyledons) swell up inside and bust it open.
You may have stalled this one. Just cover it with moist soil and wait a few days.
This is not uncommon. Soaking overnight helps soften a seed before planting.
I have been doing this for 18 years and just got some seeds from amsterdam last week. 5 of 5super lemon haze seeds popped quickly with no probs. only 2 of 5 tangerin dream seeds popped up.. They needed help because the seeds were so big and fresh.. the shell was hard to crack. I had to really super carefully help the shells bust open.. This is farther along than your seed, tho. Two of the tangerine dreams cracked open to have a root tip and then couldn't squeeze the seed open any more and got fucked up. One didn't open.
point is, I have done it a lot and things go wrong still.
Good luck and happy growing.
tommy