If the ice cream is made and packaged with machines and doesn’t come in contact with the body and hands of the workers in the process, then consuming it will not be problematic.

Also, if it actually does come in contact with them, it is still okay to consume it according to the fatwa of those scholars who don’t consider the People of the Book (Christians, Jews, etc.) as najis, although it is problematic according to those who consider them najis.

Almost all Shitte faqihs agree on the nijasah of the kuffar (non-believers)[1], but the Impurity of Ahlul Kitab (People of the Book) is an issue of dispute amongst them. The different viewpoints are as follows:

1. Nijasah of all non-Muslims among which are the Ahlul Kitab. This viewpoint was chosen by Ayatollah Golpaygani who stated and thoroughly explained about it in Nehayat al-Afkar fi Nejasah al-Kuffar, this was also Imam Khomeini’s verdict on the issue.[2]

2. Taharah of Ahlul Kitab and nijasah of the rest of the nonbelievers. This verdict has many advocates[3]. A hadith from Imam Reza confirms this fatwa.[4]

3. Taharah of all people, perceiving the nijasah of non-Muslims a result of normally making contact with a najis (impure) substance such as pork and wine, thus if they cleanse and wash themselves they will no longer be najis. Therefore, these people aren't najis per se, they become najis as a result of other najis substances.[5]

Therefore, since Hindus aren't considered People of the Book, they are najis according to the fatwa of all the maraje’, and in the case of the ice cream coming in contact with their bodies, eating it will be problematic.

So in order to correctly learn of your duty, you need to refer to your marja’s fatwa and see what his opinion is on the issue.