Thank you for the information and your question. Although it won't change things at this point, as you might expect, your decision to take a blood test was something that should have never happened. If you had spoken to an attorney ahead of time, they would have advised you to decline. It is never a good idea to "cooperate" with the police in their investigation against you. In the future always make sure they have the law on their side. In this case, since you had left the scene, they would have had to have a warrant to obtain a blood sample. In any event, that is hindsight and something to file away.
At this point, you will want to hire a local DUI attorney to represent you since you, under NH law, if you test positive for any marijuana in your system (which you are very likely to), that would be a DUI. The law is pretty extreme though and your attorney may be able to challenge the law or the presumption that you were affected by the marijuana. There may also be an issue with the sample collection, which they can investigate after they speak to you. But, assuming this is your first DUI, the sentence could be a mandatory minimum fine of $500, and between nine months and two years of license suspension. The judge may also order participation in a "drugged driving" education or treatment program.
Please do not make any statements to the police without first speaking to a local DUI attorney. They will advise you to remain silent. Feel free to ask for clarification if needed. If none is needed, then if you could take a moment to leave a positive rating in the box above, I will receive credit for assisting you today. Thank you