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Matured compost from last year is generally safe and actually useful to reuse, but it depends on how you stored it and what you put in it. If it was in a covered area, protected from excessive moisture and rain, and if you didn't add anything problematic (like treated waste or contaminated materials), you can use it without worry. In fact, recycling compost is a great practice because it maintains soil structure, adds nutrients, and improves water retention.
What you should do is check how it looks and smells before using it. If it's dark, crumbly, and smells like "good" earth, you're all set. But if you notice strange odors, see odd mold, or the soil is sticky and compacted, there might have been incomplete decomposition or water pooling - in that case it's better to let it rest a bit longer or mix it with fresh potting soil. For practical use, you can work it directly into the soil where you grow things (especially if you have a vegetable garden), or mix it in equal parts with new compost or potting soil to dilute any potential issues.
It really depends on what you had in it. I reused the compost soil from last year for my vegetable garden and it worked out fine, but I'd only put in vegetable scraps and nothing weird. If there was stuff that shouldn't be in compost though - like coated paper, animal waste - then it's better to throw it out. A good sign is the smell: if it stinks of rot and ammonia instead of damp soil, let it rest a bit longer or don't use it. If everything seems okay, just mix it with some fresh soil to dilute any excess nutrients.
The most important thing is to check the smell and appearance before using it. If the compost is dark, crumbly, and doesn't stink of rot or ammonia, you're already in good shape. If it still has a strong smell or feels sticky, it's not fully mature yet - better to wait a bit longer or mix it with fresh soil to dilute the compounds still breaking down.
One detail that often gets missed: if last year you threw in stuff treated with chemicals (coated paper, cardboard with inks, synthetic fabrics) the compost picks up those pollutants. But if it was just kitchen scraps and garden waste, reusing it is a great idea - saves money and the soil is already colonized by the right microorganisms. The only real risk is if it was in a really damp spot and grew weird molds, but you'd smell that.
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