Answer:
Yes.
Explanation:
Any source in History can be biased. It can be based on personal opinion, pressure, etc.
Let's take an example. Let's say we want to learn more about Hitler, and we have a primary source that we are analysing. The primary source is a diary entry from a Nazi propagandist, and in the diary entry he talks about how Hitler is like a reincarnation of God, he will lead Germany and the world to greatness and is all in all a great guy.
Straight away, you can tell that that is biased.
So to summarise, anything can be biased. It isn't related to what type of source it is. If you want to analyse and interpret sources, you will need to have lots of different primary and secondary sources at hand, and compare them to find the best answer and analysis.
Hope this helps
