The peg is fine. You can see the buy walls on that currency pair here: https://www.ccedk.com/nbt-btc. If the peg were failing, you would not see a buy wall.
The amount appears slightly off from $1 because it’s based on the last trade price on that pair, compared to the estimated value of BTC.
You can also check the peg support inside the Nu client. At the time of this writing, custodians are reporting about $200,000 of buy support for the peg.