Up from lying down, had aura(flashes, geometric patterns spread from middle) covering vision, mild headache and balance issue. last few secs. concern?

If this happens: repeatedly then, YES, it's a concern. If, on the other hand, it happens only once or twice, it's not much of a concern. A "head rush" can happen when standing upright from a sitting or crouching position if the heart & blood vessels haven't had a chance to accommodate to the change in posture. Dehydration, overheating & certain other conditions can contribute to head rushes.