Interference call.
1st base runner going to 2nd base rounding 2nd runs into ss at 2nd base.
runner stops and returns to 2nd base instead of continuing to 3rd.(umpire seeing the contact puts his arm out)
after runner returns to base umpire calls time out.
Does the runner automatically get awarded 3rd base?
I could not find any ruling on this play.

This is an "obstruction" call, not an "interference" call, which may have been why you had some difficulty finding the appropriate ruling ... No worries, though ... You're not the first, and won't be the last, person who confused those terms! ... Please see the SSUSA Rulebook page 49 to see how this umpire's judgment call fits with the fact pattern you observed ...
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§8.4(10) • WHEN RUNNERS ARE ENTITLED TO ADVANCE
Runners are entitled to advance without liability to be put out:
A. When a fielder obstructs the progress of a runner or batter-runner, who is legally running the bases. NOTE: Obstructed runners are still required to touch all bases in proper order, or they could be called out on a proper appeal by the defensive team. Should an act of interference occur after any obstruction, enforcement of the interference penalty would have precedence. EFFECT: When obstruction occurs, the umpire shall call "obstruction" and give a delayed dead ball signal for obstruction. NOTE: Failure of the umpire to call obstruction DOES NOT negate the obstruction.

4. When a runner, while advancing or returning to a base, is obstructed by a fielder who neither has the ball nor is attempting to field a batted or thrown ball, or a fielder who fakes a tag without the ball, the obstructed runner and each other runner affected by the obstruction will always be awarded the base or bases that would have been reached, in the umpire's judgment, had there been no obstruction. If the umpire feels there is justification, a defensive player making a fake tag could be ejected from the game.