You can buy and sell Bitcoin with fiat, but you can't use them to pay for
anything. For as long as you don't use them to purchase goods/services, you should be fine.
Source:
The regulation, however, only prohibits the use of cryptocurrencies as a payment tool, and does not regulate activities such as bitcoin mining and trading.
As a sidenote, you can't use
any foreign currency to buy anything within the country in normal circumstances either, so this isn't specific to Bitcoins or crypto. The Rupiah is their
only legal tender.