Iran has not made a nuclear bomb.
Iran's economy is in ruins due to sanctions we have placed since 1979.
Iran is a primarily Shiite country. Somalia is a Sunni one. Sunni's and Shii are enemies.
What you mean to ask is why aren't rich Sunni nations like Turkey and Saudi Arabia and the rest of them feeding and assisting those and other Sunni refugees.
Remember, a century ago, Syrians were called Turks because they were part of that country.
Incidentally, Iran has taken in the highest number refugees in the world, primarily from neighboring Afganistan and also Iraq, as well as Armenia from when the Ottaman Empire tried to exterminate them.
As you know, Armenia is the world's oldest Christian country, and today, Iran is it's closest ally and supporter, as well as economic partner.