Is it possible to store an array in Django model?

Yes, you can use it like this:

from django.contrib.postgres.fields import ArrayField
class Board(models.Model):
    pieces = ArrayField(ArrayField(models.IntegerField()))

However, it can only be available when using PostgreSQL for the database.

If you aren't using Postgres, I recommend Django's validate_comma_separated_integer_list validator.

https://docs.djangoproject.com/en/dev/ref/validators/#django.core.validators.validate_comma_separated_integer_list

You use is as a validator on a CharField().

I'd have two advices for you:

1) Use ArrayField if you are using PostgreSQL as your database. You can read more about ArrayField here.

2) Encode your array as JSON and store it either as a plain string or using a JSONField as found here.

I'd personally prefer option number 1 since that is the cleaner and nicer way but depending on what you are actually using to store your data that might not be available to you.