A company is using my idea internally!

In the US, like most countries with patent systems, it is illegal to use an invention claimed in a patent without a license. In some countries, the government will grant an injunction against such users if you show evidence of the infringement to a court. In the US, at least in high-tech fields (bio/pharma might be different), injunctions are rare since the Ebay v MercExchange case. If you win a lawsuit, you are likely to be awarded the amount of money you would have gotten if you and the user had negotiated a license before they began using the invention. Such a license generally involves a royalty payment on their marginal profit from using the invention.

So, once you have your granted patent in hand, you ought to consider how much more profit are is the user making by using your invention than they would make without using your invention. A small portion of that difference, as a royalty, is what you could get if you win a lawsuit. If that is greater than the cost of the lawsuit then you should ask them to negotiate a license agreement and pay you a royalty. Otherwise, it is probably not worthwhile for you to do anything.

Of course, every situation is different. You might want to consult a knowledgeable attorney about your case.

Is your patent only filed in the USA? Has it actually been granted or is going through the search and examination phase ?

Be aware that you have to prove they did not use your idea before your filing date. You have to porovde that they used your idea after it was pubished.

How long has your patent been granted. If your patent is relatvely new when was it filed as they could file observations that could destroy your patent (depending how new it is and how far into the patent process you are if your patent is still in the search and examination phase).

you say " I guess SOMEHOW they ran into this issue and to continue operation came up with and idea that infringe mine"

That could be perceived as grounds for saying your idea was "obvious to someone skilled in the art" i.e: it is a problem that only has an one obvious solution ?

Do you know when they started using your idea and can you substantiate this. It could end up a your word against their corporate lawyers' and that could be expensive and lengthy. I have seen these things drag on for up to 6 years and there is only one winner and that is not the patentee or the infringer !!

Good luck

Logikman