OK.. Your toe is open..
you cast on X (say 16) and joined into a round--and started knitting?
or are your increases too open? (i like a raised increase for shaping toe up socks--i think its the tightest/neatest..but that is MHO)
If you started with long tail, the answers is:
you'll have to sew up the open cast on. (use the tail, and for this application, whip stitch it closed--then turn around and whip stitch it again, making a nice cross stitch line at the tip of the toe.
Next time, consider your cast on--there are lots of cast ons besides Long Tail...
for toe up I am a fan of Judy's Magic Cast on.. (see YouTube/Cat Bordhi's demo to learn)
but i've also used, a figure 8, and turkish/(aka eastern) cast on.. (see Knitty.com for demos)
Or try the short row toe..
Cast on X (1/2 of total desired # of stitches+1)
USE a simple or Use a Provisional cast on.
DECREASE or short row till you have about 1/3rd or original #--ie, if you NEED 60 stitches, cast on 30 +1 (31)
decrease/ short row till you have 10 (or about 1/3 of 30 )
(2 decreases ever other row, or 1 decrease each edge)
then INCREASE by picking up (one stitch each in each edge of the previous knit toe half )till you once again have 30..
If you did short rows, just pick up 1 stitch at each edge every row..
then pick up stitches from cast on edge, (or undo provisional cast on, and use live stitches. --you'll only be able to pick up 30--
round 1, correct count by K2tog.
(If you decrease in stead of doing short rows, you would have:
R1: sl 1, k1, K2tog knit rest of row
R2: Sl1, P1, P2tog, purl rest of row.
And then increased by:
Pick up stitch in first Chain (s1)--Knit row
at end of row, Pick up stitch in first chain on other edge
R2: slip the just picked up stitch, Purl row
Just be sure to work your way up the ladder of chains..each knit row, with 1 stitch picked up in each chain stitch.(2 total, one pick up on each edge)