What is the correct way to check for "possibly null" references?

I have this bit of relevant code:

if (boardMap[i,j] != null) {
    Console.Write(boardMap[i,j].color.ToString() + " " + boardMap[i,j].type.ToString());    
}
else {
    Console.Write("X");
}

boardMap contains potentially null values, which is why I implemented the if statement checking if the boardMap[i,j] item is null. However, I get a warning in line 2 telling me that boardMap[i,j] is possibly null.
How do I fix this -> What is the correct way to do null checks like this?

(Please note, I am very much a beginner with dotnet and C#)

>Solution :

As of C# 8.0 and later, you can use the null-forgiving operator. Just append ! after whatever might be null. It basically tells the compiler that it should turn off possibly null warnings for this occurrence.

if (boardMap[i,j] != null) {
    Console.Write(boardMap[i,j]!.color.ToString() + " " + boardMap[i,j]!.type.ToString());    
}
else {
    Console.Write("X");
}