I think one effect this will have in a relatively rapid time period is great innovation in seafaring. I read an article on seafaring in the pre-Columbian Caribbean which quoted a conquistador saying that before they got iron axes from the Spanish, it took the Indians days just to cut down a tree big enough to make a seagoing canoe from. The ability to rapidly cut down very large trees will encourage more boatbuilding and give more room for innovation. This assumes that ironworking is widespread enough to use to make tools, as opposed to prestige items.
I don't think ironworking in a vacuum will change that much about warfare. Without an equivalent to cavalry, there isn't a lot of pressure to drill troops and fight in formation in the European style. Iron slashing and stabbing weapons may still supplant clubs though, which will in turn force innovation in armor. IOTL the Inca had woven armor that was very effective against clubs, but faced with swords they may add a layer of something new, such as a form of brigandine armor (metal-studded hardened leather).