I would like to ask whether attending a workshop in IROS is significant, I had a paper, but what I heard that they accept the contribution without being peer reviewed.

If I am going to attend, it going to cost me money as I am not financially supported! I am confused whether I have to go or it is not significant?

Conferences are different levels. Maybe this is not a top conference but maybe it is also not a low level one. I do not know all conferences in my field and of course my knowledge is less in other fields.
Attending the workshop has many advantages. First, the paper will be available in the proceedings. Second, this might be your heighst honour and might be your marketing key for applying for PhDs. When I started to apply for PhD, I wished I had a paper even in a crap conference. I had back then written in my CV the name of the paper I have "reviewed".
To conclude, if you can afford to pay the fees, it is definitely worth.