traffic lights query

hi all,
first post so hope its in right section. at traffic lights, if i cross the white stop line while the lights are on green and i am waiting before the yellow junction box because the exit is not clear and as it clears i enter and carry on through to my exit, do i have right of way over cars coming from the side junction to the left? my thoughts are that they should wait until i am clear before they go, and not try to get in front of me as i have right of way.