YES!! Because you have both a main phase 1 and a main phase 2. If you do not summon a monster in main phase 1, enter your battle phase, complete your battle phase, then enter your main phase 2 and you can summon a monster with 4 stars or less unless it has a special effect or tribute the monster that already attacked. Unfortunately you will not be able to attack with the new monster until the next turn, but hey, thems the breaks.